Transportation & Other Facilities Management - USDA Forest Service

R-10 AMENDMENT 2509.22-2006-2
EFFECTIVE DATE: 07/14/2006
DURATION: This amendment is effective until superseded or removed.
FSH 2509.22 – SOIL AND WATER CONSERVATION HANDBOOK
CHAPTER 10 – WATER QUALITY MANAGEMENT FOR
NATIONAL FOREST SYSTEM LANDS IN ALASKA
2509.22_10
Page 73 of 117
the surface materials, is encouraged and may be required where rock durability tests
indicate excessive breakdown of road surface rock will occur.
b. Construct and maintain water bars on roads to be closed. Water bars are a
combination of excavation and mounding of road construction materials, located and
designed to divert and disperse water from the road surface. If water bars are
designed and constructed to allow high clearance vehicle access, they must be
maintained.
c. Employ regular inspection, maintenance, rolling grades, in sloping, out sloping,
and other treatments to limit the length of water movement down running surfaces or
make surface materials less susceptible to detachment.
4. REFERENCES. FSM 7706.11, 7706.12, 7706.13, and 7720; 1985 Forest Service
Specifications, EM-7720-100 R and EM 7720-100B; Standard Specifications 50.4, 203, 204,
206A, 210, 212, 412, 619, 625, 626, 629, and 630; Alaska Region Special Project Specifications
for the Construction of Roads, Bridges and other Drainage Structures; T-Specifications for Road
Maintenance; Timber Sale Contract Provisions B(T)6.31, B(T)6.6, B(T)6.62, B(T)6.65,
B(T)6.66, C(T)5.2, C(T)5.4, C(T)5.411#, C(T)5.412, C(T)6.6, and C(T)6.62; FSH 2409.15.
14.9 – PRACTICE: Drainage Control to Minimize Erosion and Sedimentation
1. OBJECTIVE. To minimize the erosive effects of concentrated water flows from
transportation facilities and the resulting degradation of water quality through proper design, and
construction of drainage control systems.
2. EXPLANATION. This is an administrative and preventive practice. Stabilizing the
road prism and adjacent disturbed areas can minimize degradation of water quality from
sediment generated by the erosive effects of surface runoff. Velocities in the ditches and cross
drain culverts can be dissipated before entry into the natural system by design and construction
of control structures (see BMP 14.14 and 14.17 for stream crossings and in-channel operations).
A number of measures can be used alone or in combination to control erosion in ditches and at
culvert outlets. Methods used to control water and reduce erosion may include: properly spaced
and sized culverts, catch basins, ditch-blocks, cross drains, water bars, rolling dips, energy
dissipaters, aprons, gabions, and armoring of ditches and drain inlets and outlets. Dispersal of
runoff can also be accomplished by rolling the grade, crowning, in sloping, out sloping, or
installation of water spreading ditches. The following measures are generally applicable:
a. Riprap culvert inlets and outlets as needed to prevent erosion of the road prism.
Velocity dissipation at cross drain culvert outfalls is required to limit erosion and
undermining of the road fill.
b. Utilize relief culverts as necessary to disperse road runoff and minimize ditch
erosion or saturation of road fills. Maintain natural drainage patterns to the extent
practicable.